Water resistance ratings explained

Why 30 m does not mean thirty metres.

The ratings are static test pressures

A depth rating is a laboratory pressure figure, not a swimming depth. Movement through water adds dynamic pressure well beyond the static equivalent, which is why 30 m is a splash rating and 100 m is the sensible minimum for swimming.

Gaskets are consumables

Rubber gaskets compress and harden with age and heat. A pressure test costs very little and should be repeated whenever the case is opened or every couple of years for a watch that gets wet.

The crown is the weak point

A screw-down crown left unscrewed defeats the entire system. Push-pull crowns rely entirely on gasket compression, so they are the first thing to fail on a vintage watch.

Heat is the real enemy

Hot showers and saunas expand the case and gaskets at different rates and drive moisture in. Chlorine and salt degrade gaskets and seals faster than fresh water; rinse and dry after either.

How Chrono24 Watches applies this

Every watch we list is opened and inspected before it appears on the site. We verify the calibre against the reference, examine dial printing and lume ageing under magnification, record timing across multiple positions on a calibrated timegrapher, measure bracelet stretch, and pressure-test sports references with intact cases. What we find is published on the listing, including the flaws, and photographed. You can read the full process on our authentication page.

Buying with confidence

Shipping is free, fully insured and requires a signature on delivery. You have fourteen days from delivery to return any watch for a full refund, for any reason, using a prepaid insured label, and every mechanical watch carries a twelve-month warranty on the movement. Our authenticity guarantee has no expiry date. If this is your first purchase from us, start with how to buy.

Next steps

Start with the full catalogue, read our authentication process, or email sales@chrono24watches.st with any question about a specific listing.